An in-vehicle navigation apparatus uses radio navigation and self-contained navigation to detect a current position of the vehicle. In the self-contained navigation, a current position is estimated from values detected by a vehicle speed sensor and a bearing sensor (e.g., geomagnetic sensor and gyroscope); the estimated current position is collated with road map information (hereinafter, this process is called map-matching) to designate a current position. In the radio navigation, a current position is estimated based on radio waves from satellites; the estimated current position is also subjected to map-matching to designate a current position. To more accurately designate a current position, both the radio navigation and self-contained navigation are used.
A map-matching technology considering roads' traffic directions is described in an in-vehicle navigation apparatus in Patent Document 1. Two roads parallel to each other less than a given interval therebetween may be located around a current position estimated from sensors. Here, of the two roads, a road located left relative to a vehicle's advancing direction is subjected to map-matching: in a two-way expressway in the Japanese traffic system has two one-way traffic roads parallel to each other, a road located left relative to the vehicle's advancing direction is typically trafficable for the vehicle. The navigation apparatus in Patent Document 1 is thus able to accurately designate a current position even if the vehicle travels one of two one-way traffic roads parallel to each other.
However, vehicles do not always travel a left road of two parallel roads because of recent complexity in road configuration. A recent in-vehicle navigation apparatus has one-way traffic information indicating a trafficable direction in road data of a link corresponding to a one-way traffic road. With the indicated trafficable direction and advancing direction considered in map-matching, a current position of the vehicle is designated.
Even a one-way traffic road may be temporarily used in a direction opposite to its original trafficable direction because of roadworks or the like. Here, the trafficable direction indicated by the road data of a certain one-way traffic road cannot be used properly for map-matching: if a vehicle travels the certain one-way traffic road in the direction opposite to the original trafficable direction, the certain one-way traffic road cannot be designated in the map-matching. A nearby road might be mistakenly designated or no road can be designated.                Patent Document 1: JP-H8-145706 A        